The main structure of a liquid crystal display (LCD) comprises an array substrate and a color filter substrate arranged opposite to each other; a pixel matrix and a peripheral circuit are formed on the array substrate; the pixel matrix includes a plurality of pixel regions; each pixel region includes a transparent pixel electrode; and RGB color filters and a transparent common electrode, corresponding to the transparent pixel electrode in position, are formed on the color filter substrate. Patterns on the array substrate and the color filter substrate are usually formed through mask patterning processes. In a patterning process, photoresist is coated on a substrate. In order to ensure the exposure effect, the quantitative supply of the photoresist must be achieved.
As illustrated in FIG. 3, a traditional automatic photoresist supply device includes a gas passage 1 and a fluid passage 2 for photoresist passing through; a supply container 3 for accommodating photoresist is disposed within a sealing tank 4; the gas passage 1 is communicated with the sealing tank 4; one end of the fluid passage 2 is disposed in the supply container 3; and the photoresist in the supply container 3 is ejected via a nozzle 7 at the other end of the fluid passage 2 by a pneumatic device by continuously introducing gas 20 (e.g., industrial nitrogen) into the sealing tank 4, and then is coated on the substrate. The specific process of achieving the quantitative photoresist supply by the device is conducted as follows:
At the beginning, the time variable parameters are acquired at the end of the gas passage 1. An electromagnetic valve 5 is disposed on the gas passage 1, and a position sensor 10 is disposed at the nozzle 7 of the photoresist. When the position sensor 10 senses that the substrate is disposed at a proper position of the device by a manipulator so as to be coated with the photoresist, ejection of photoresist is triggered. At this point, the electromagnetic valve 5 is switched on by a control device 8, and the timing process begins.
Subsequently, the quantitative photoresist supply is conducted by the control device 8 to control the supply time period every time. When the timing moment arrives, the electromagnetic valve 5 is switched off by the control device 8 so as to cut off the gas passage 1.
Moreover, the device usually requires a deflation passage 9; one end of the deflation passage is communicated with the sealing tank 4; and an electromagnetic valve 6 is disposed in the midst of the passage. Upon quantitative photoresist supply, the electromagnetic valve 6 is switched off; and after quantitative photoresist supply each time, the electromagnetic valve 6 is switched on by the control device 8 so as to deflate for a period of time (usually 3 to 5 seconds), and hence the pressure in the sealing tank 4 can be restored to the atmospheric pressure.
But along with the increase of supply frequency, the gas space in the sealing tank is widened due to the reduction of the liquid level in the container; and the outlet liquid level of supplied liquid is relatively higher, and hence the amount of photoresist ejected within same ejection time is reduced. The variation is obvious according to the measurement, so that the accuracy requirement of quantitative photoresist supply cannot be satisfied.